1. Field of the Invention
The present invention relates to repair and reconstruction of tunnels, sewers and other structures referred to herein as conduits, which have deteriorated due to age and are in need for reconstruction which includes both waterproofing and strengthening of the internal structure.
2. Description of Related Art
Tunnels and particularly sewer structures in the U.S. and throughout the world are frequently deteriorated to the point where they do not retain the liquids and other effluent they need to contain; often, they do not exclude ground water from entering or lose their structural capability. These normally brick or masonry structures require repairs which necessitate replacement of the masonry structure with a new one. This requires digging up of the old sewer structure, removing the old materials and replacing the brick or concrete sewer line with a new one made of similar materials. All of this involves enormous cost and disruption of pedestrian or vehicular traffic since many sewer lines are buried under streets or sidewalks in cities.
The problem is particularly acute for the larger sewer lines which have to be built up in place, in contrast to smaller sewer lines which can be preformed pipe-like elements laid end-to-end.
There have been various attempts to rebuild these types of sewer lines utilizing plastic liners. One example is U.S. Pat. No. 4,585,371, to Jones-Hinton. This patent shows a sewer liner composed of two types of longitudinal plastic shapes linked edge-to-edge to form an approximately semi-circular tunnel liner open at the bottom. This liner is formed of rib-like elements or spacer elements located between and interlocked with the side members of the relatively wider, flat lining elements which, when in position, form the liner wall of the assembly. When in place, a settable liquid or semi-liquid compound is injected into the longitudinal end openings or hollow portions of lining elements to strengthen and stiffen them. In addition, the settable compound can be injected separately between the inner surface of the sewer to be repaired and the outer surface of liner elements to fill in the space between the various rib-like elements and the tunnel to be repaired. Since the whole liner structure of Jones-Hinton loosely contacts the tunnel liner and the whole assembly is not fastened to and is allowed to move within the tunnel, there is no seal between the settable compound when set and the structure composed of spacer elements and lining elements or with the tunnel wall. Other problems are apparent from the statement in this reference that the lubricants must be introduced to slidably assemble the elements together. This would create extensive problems since these elements, when put in place in the sewer to be repaired, might be many feet long, perhaps 50' to 200' in length, requiring sliding of the elements within each other the whole distance. Other deficiencies are obvious in that the bottom of the whole structure is open, thereby not functioning to retain sewer liquids or exclude ground water, in addition to not having significant structural strength to reinforce the weakened physical structure of the deteriorated sewer.
Another prior effort is illustrated by U.S. Pat. No. 4,366,012. This patent discloses lining a sewer to be repaired with a tube of felt with an impervious plastic outer layer, applying a "slug" of resin to the inner tube of fibrous felt-like material and drawing the tube through squeezing rollers while a vacuum is drawn through one or more openings in advance of the spreading resin. The process involved placing a measured quantity of semi-liquid settable plastic at the end of the tunnel segment to be repaired, spreading the settable plastic through the inner fibrous tube sequentially from the far portion to the near portion by using rollers and drawing air from the fiber tube.